Treatment for improving cellulose insulation

ABSTRACT

A method for manufacturing a fire retardant cellulose insulation with reduced density and reduced settling. The method consists of adding a material, the fibers of which have a positive electrostatic charge, onto a shredded newspaper base either before or after the addition of a pre-coat, consisting of a mixture of limestone and an antistat. A fire retardant agent is then added and the materials are ground in a finish mill. The newspaper fibers become positioned at an angle to the paper pieces, increasing the distance between the paper pieces, thereby lowering the density of the cellulose. Fibers such as ground cardboard, wood mulch, sawdust, fiberglass fibers and polyester fibers, are examples of materials with electrostatically positively charged fibers.

TECHNICAL FIELD

[0001] This invention relates generally to cellulose insulation of thetype utilizing a shredded newspaper base which is treated with a fireretardant chemical composition and used for the thermal insulation ofhomes and other building structures. More particularly, the inventionrelates to the addition of a specific range of antistat andelectrostatically positively charged fibrous materials to the newspaperbase which will lower density and reduce settling of the insulation.

BACKGROUND ART

[0002] The manufacture of cellulosic insulation, in accordance with thepresent state of the art, begins with a grinding operation in whichnewspapers are shredded to a level of approximately 1″×1″ pieces andindividual fibers. These fibers and paper pieces, carried in air stream,are then ground in a second operation in which finely ground fireretardant chemical is added to the paper and paper pieces.

[0003] The key to the understanding of the underlying basis of celluloseinsulation is to recognize that cellulose insulation is made up ofnewspaper pieces and fibers which are affected by static electricity.Like elements will repel; unlike elements will attract. A method ofdetermining the electrostatic charge of a material piece or fiber is torub the flat side of a nylon toothbrush about 50 times on a piece ofwool. Then attempt to attract the material in question with the flatside of the toothbrush. If the material is positively charged, it willattach to the flat part of the toothbrush. If the material is negativelycharged, it will not be attracted. Based on the above system, the faceof a newsprint paper piece is positively charged and the edge fibers arenegatively charged. The newspaper separate fibers are also negativelycharged.

[0004] U.S. Pat. No. 4,468,336 refers to an insulation “wherein theloose fill cellulose insulation has a settled density on the order ofabout 2.5 pounds per cubic foot before mixing with staple fibers, andthe mixture of cellulosic insulation with from 2% to 25% by weightstaple fibers has a settled density in the order from 2.1 pounds percubic foot to about 1.1 pounds per cubic foot. Staple fibers weredefined as acrylic, polypropylene, acetate etc. These fibers areelectrostatically positively charged.

[0005] Because the paper pieces were positively charged, the surface ofthe paper piece attracted negatively charged paper fibers, essentiallyparallel to the face of the paper piece. This attraction caused thepaper piece to become neutrally charged and therefore, no longerstatically attractive. Therefore, the positively charged staple fibersattracted most of the remainder of negatively charged paper fibers,forming a phase separate from the paper pieces. This separate phase isnot settling stable because this structure is not supported by the paperpieces and will condense. It took a large amount of the staple fibers tolower the cellulose density by producing a separate, lower density,paper fiber to positively charged fiber structure.

BRIEF DESCRIPTION OF INVENTION

[0006] In an attempt to improve settling and density of celluloseinsulation, I determined that there was an advantage to produce aspecific type of fiber-paper piece structure. In this structure, use ofthe limestone-antistat mixture as described in U.S. Pat. Nos. 5,399,375and 5,455,065, in a narrow dosage range, reduces the static charge onthe paper pieces and fibers to a level where fire retardant chemicalwill adhere to both the paper pieces and fibers. The preferred structureis where the fibers are attached to the paper piece at an angle to theface of the paper piece, not parallel to the face of the paper piece. Inthis preferred structure, there is very little separate fiber to fibergroupings.

[0007] Electrostatically positively charged fibers such as wood,fiberglass or polyester, added either before or after the addition ofthe antistat to the partially ground paper, are attracted to thenegative edges of the electrostatically charged paper piece. Theattached positively charged fibers then attract the negatively chargedpaper fibers, producing a reinforced structure which reduces density andsettling.

[0008] These improvements in density and settling result from the factthat the negative fibers are deposited at an angle to the face of thepaper piece. The amount of electrostatically positively charged fibersadded will vary with the type of fiber used. The key is that the amountof separate, positively charged fibers to negatively charged fibergroupings is held to a minimum.

[0009] The following convention will be used. Newspaper pieces, woodfibers, cardboard fibers, fiberglass fibers and polyester fibers arepositively charged. Newspaper fibers and cardboard pieces are negativelycharged. The relationship of the positively charged fibers to thenegatively charged paper fibers can only be understood by using a highpowered microscope.

DETAILED DESCRIPTION

[0010] The amount of wood fiber necessary to reinforce the paperpiece/paper fiber structure is in the range of 2% to 8% of the weight ofthe paper and positive electrostatic fiber input. The amount offiberglass fiber and polyester fiber to reinforce the settling stablestructure is in the range of 0.5% to 2% of the paper and positiveelectrostatic fiber input. The preferred amount of electrostaticpositively charged reinforcing fibers is determined by the structureachieved, as seen using a high powered microscope.

[0011] The anti-static constituent of the precoat mixture of antistatand finely ground limestone is preferably on the order of 0.001% to0.002% by weight of the paper and positive electrostatic fiber input.The limestone component range is 1% to 2% of the weight of paper andpositive electrostatic fiber input. Other fine ground additives may beused in place of the limestone, but fire retardancy will be decreased.This range of antistat reduces the static charges of the paper pieces,paper fibers and electrostatically positively charged fibers so thatpositively charged fine ground fire retardant chemicals will adhere tothe paper pieces, paper fibers and electrostatically positively chargedfibers.

[0012] In this range, the fibers will attach, essentially at an angle tothe paper pieces, causing a greater distance between paper pieces and alower density. Antistat levels above this range will reduce the staticcharges so that the attachment of fibers to the paper pieces will bediminished and paper fiber to electrostatically positive fiber groupingswill occur, reducing the settling stability effect. Antistat levelsbelow this range will tend to inhibit the attachment of fire retardantchemical to the paper pieces, reducing fire retardancy.

EXAMPLE 1.

[0013] A trial was made using 95% newspaper and 5% sawdust. Thenewspaper was ground in a shredder to a size of about 1″×1″. A precoatmixture was then added to the shredded newspaper, the precoat containingdimethyl distearyl ammonium chloride in the amount of 0.0015%, combinedwith limestone in the amount of 1.5% of the weight of paper and positiveelectrostatic fiber input. Sawdust in the amount of 5% of the weight ofpaper and positive electrostatic fiber input was then added. Thesematerials were fed in an air stream into a finish mill along with 10% ofa finely ground fire retardant chemical, based on the total weight ofthe system.

[0014] The initial material had a density of 0.70 lbs./cu.ft. Thismaterial was placed in a 12″×12″×6″ high cardboard box in an atmosphereof 50% relative humidity and 70 degrees F. for a period of one month.Settling was 8% after one month.

[0015] Commercial cellulose, not containing the sawdust or antistat,under the same conditions as above, had an initial density of 1.3lbs./cu.ft and settled 16% over the same period.

EXAMPLE 2

[0016] A trial was made similar to Example 1 but the sawdust was firstcombined with the newspaper base before the addition of the limestoneantistat mixture. Under conditions similar to Example 1, settling after30 days was 12% after one month and initial density was 0.80 lbs./cu.ft.

EXAMPLE 3

[0017] A trial was made similar to Example 1 but 2% fiberglass wassubstituted for the sawdust used in Example 1. Under conditions similarto Example1, settling after 30 days was 7% and density was 0.75lbs./cu.ft.

EXAMPLE 4

[0018] A trial was made similar to Example 2 but 2% fiberglass wassubstituted for the sawdust used in Example 2. Under conditions similarto example 2, settling was 9% and density was 0.81 lbs./cu.ft.

EXAMPLE 5

[0019] A trial was made similar to Example 1 but 1% polyester fiberswere substituted for the sawdust used in Example 1. Under conditionssimilar to Example 1, settling after 30 days was 8% and density was 0.78lbs./cu.ft.

EXAMPLE 6

[0020] A trial was made similar to Example 2 but 1% polyester fiberswere substituted for the sawdust used in Example 2. Under conditionssimilar to Example 2, settling after 30 days was 12% and density was0.87 lbs./cu.ft.

1. An improved cellulosic insulation having reduced density and settlingcomprising (a) shredded cellulosic fibers and paper pieces which areprecoated with a mixture of limestone and an antistatic agent eitherbefore or after the addition of (b) electrostatically positively chargedfibers and (c) fire retardant chemicals which are adhered on saidshredded cellulosic fibers, electrostatically positively charged fibersand paper pieces.
 2. An insulation in accordance with claim wherein saidanti-static agent is a quaternary ammonium compound.
 3. An insulation inaccordance with claim 1 wherein said insulation comprises substantially0.001% to 0.002% by weight of said antistatic agent, based on the weightof cellulosic fibers, paper pieces and positive electrostatic fiberinput.
 4. An insulation in accordance with claim 1 wherein said mixtureof antistat and limestone comprises substantially 1% to 2% of the weightof cellulosic fibers, paper pieces and electrostatic positively chargedfibers.
 5. An insulation in accordance with claim 1 wherein saidinsulation comprises positively charged electrostatic fibers such aswood fibers, shredded cardboard, wood mulch and sawdust at a level ofsubstantially 2% to 8% of the weight of cellulosic fibers, paper piecesand electrostatic positively charged fibers.
 6. An insulation inaccordance with claim 1 wherein said insulation comprises positivelycharged electrostatic fibers such as fiberglass or polyester fibers at alevel of substantially 0.5% to 2% of the weight of cellulosic fibers,paper pieces and electrostatic positively charged fibers.
 7. Aninsulation in accordance with claim 1 wherein the electrostaticallynegative paper fibers are angled predominantly from about 15% toperpendicular to the surface of the paper pieces.
 8. A method formanufacturing fire retardant cellulosic insulation of the typecomprising shredded cellulosic fibers precoated with a mixture oflimestone and an antistatic agent and having a fire retardant agentdeposited on it wherein the improvement comprises adding a positivelycharged electrostatic fiber either before or after the addition of themixture of limestone and an antistatic agent.
 9. A method in accordancewith claim 8 wherein positively charged electrostatic fibers such asground cardboard, wood mulch, and sawdust are added in the amount ofsubstantially 2% to 8% of the weight of the cellulosic fibers, paperpieces and electrostatic positively charged fibers.
 10. A method inaccordance with claim 8 wherein positively charged electrostatic fiberssuch as fiberglass or polyester are added substantially in the amount of0.5% to 2% of the weight of cellulosic fiber, paper pieces andelectrostatic positively charged fibers.